Buggy code:
final int getFlushDeletesCount ( ) { } final String newSegmentName ( ) { } private PrintStream infoStream ; private static PrintStream defaultInfoStream ; @ Deprecated public void optimize ( ) throws IOException , CorruptIndexException { } @ Deprecated public void optimize ( int maxNumSegments ) throws IOException , CorruptIndexException { } @ Deprecated public void optimize ( boolean doWait ) throws IOException , CorruptIndexException { } public void forceMerge ( int maxNumSegments ) throws IOException , CorruptIndexException { } public void forceMerge ( int maxNumSegments , boolean doWait ) throws IOException , CorruptIndexException { } private synchronized boolean maxNumSegmentsMergesPending ( ) { } @ Deprecated public void expungeDeletes ( boolean doWait ) throws IOException , CorruptIndexException { } public void forceMergeDeletes ( boolean doWait ) throws IOException , CorruptIndexException { } @ Deprecated public void expungeDeletes ( ) throws IOException , CorruptIndexException { } public void forceMergeDeletes ( ) throws IOException , CorruptIndexException { } public final void maybeMerge ( ) throws IOException , CorruptIndexException { } private final void maybeMerge ( int maxNumSegments ) throws IOException , CorruptIndexException { } private synchronized void updatePendingMerges ( int maxNumSegments ) throws IOException , CorruptIndexException { } public synchronized Collection < SegmentInfo > getMergingSegments ( ) { } public synchronized OneMerge getNextMerge ( ) { } public void rollback ( ) throws IOException { } private void rollbackInternal ( ) throws IOException { } public synchronized void deleteAll ( ) throws IOException { } private synchronized void finishMerges ( boolean waitForMerges ) throws IOException { } public synchronized void waitForMerges ( ) { } synchronized void checkpoint ( ) throws IOException { } private synchronized void resetMergeExceptions ( ) { } private void noDupDirs ( Directory ... dirs ) { } @ Deprecated public void addIndexesNoOptimize ( Directory ... dirs ) throws IOException , CorruptIndexException { } public void addIndexes ( Directory ... dirs ) throws IOException , CorruptIndexException { } public void addIndexes ( IndexReader ... readers ) throws IOException , CorruptIndexException { } private void copySegmentAsIs ( SegmentInfo info , String segName , Map < String , String > dsNames , Set < String > dsFilesCopied ) throws IOException { } protected void doAfterFlush ( ) throws IOException { } protected void doBeforeFlush ( ) throws IOException { } public final void prepareCommit ( ) throws IOException , CorruptIndexException { } public final void prepareCommit ( Map < String , String > commitUserData ) throws IOException , CorruptIndexException { } private final Object commitLock = new Object ( ) ; public final void commit ( ) throws IOException , CorruptIndexException { } public final void commit ( Map < String , String > commitUserData ) throws IOException , CorruptIndexException { } private final void commitInternal ( Map < String , String > commitUserData ) throws IOException , CorruptIndexException { } private final synchronized void finishCommit ( ) throws IOException , CorruptIndexException { } protected final void flush ( boolean triggerMerge , boolean flushDocStores , boolean flushDeletes ) throws IOException , CorruptIndexException { } protected final void flush ( boolean triggerMerge , boolean applyAllDeletes ) throws IOException , CorruptIndexException { } private synchronized boolean doFlush ( boolean applyAllDeletes ) throws IOException , CorruptIndexException { } public final long ramSizeInBytes ( ) { } public final synchronized int numRamDocs ( ) { } private void ensureValidMerge ( MergePolicy . OneMerge merge ) throws IOException { } private synchronized void commitMergedDeletes ( MergePolicy . OneMerge merge , SegmentReader mergedReader ) throws IOException { } private synchronized boolean commitMerge ( MergePolicy . OneMerge merge , SegmentReader mergedReader ) throws IOException { } private final void handleMergeException ( Throwable t , MergePolicy . OneMerge merge ) throws IOException { } public void merge ( MergePolicy . OneMerge merge ) throws IOException , CorruptIndexException { boolean success = false ; final long t0 = System . currentTimeMillis ( ) ; try { try { try { mergeInit ( merge ) ; if ( ( infoStream ) != null ) <START_BUG> message ( ( ( ( ( ( "now<seq2seq4repair_space>merge\n<seq2seq4repair_space>merge=" + ( merge . segString ( directory ) ) ) + "\n<seq2seq4repair_space>merge=" ) + merge ) + "\n<seq2seq4repair_space>index=" ) + ( segString ( ) ) ) ) ; <END_BUG> mergeMiddle ( merge ) ; mergeSuccess ( merge ) ; success = true ; } catch ( Throwable t ) { handleMergeException ( t , merge ) ; } } finally { synchronized ( this ) { mergeFinish ( merge ) ; if ( ! success ) { if ( ( infoStream ) != null ) message ( "hit<seq2seq4repair_space>exception<seq2seq4repair_space>during<seq2seq4repair_space>merge" ) ; if ( ( ( merge . info ) != null ) && ( ! ( segmentInfos . contains ( merge . info ) ) ) ) deleter . refresh ( merge . info . name ) ; } if ( ( success && ( ! ( merge . isAborted ( ) ) ) ) && ( ( ( merge . maxNumSegments ) != ( - 1 ) ) || ( ( ! ( closed ) ) && ( ! ( closing ) ) ) ) ) { updatePendingMerges ( merge . maxNumSegments ) ; } } } } catch ( OutOfMemoryError oom ) { handleOOM ( oom , "merge" ) ; } if ( ( ( infoStream ) != null ) && ( ( merge . info ) != null ) ) { message ( ( ( ( ( "merge<seq2seq4repair_space>time<seq2seq4repair_space>" + ( ( System . currentTimeMillis ( ) ) - t0 ) ) + "<seq2seq4repair_space>msec<seq2seq4repair_space>for<seq2seq4repair_space>" ) + ( merge . info . docCount ) ) + "<seq2seq4repair_space>docs" ) ) ; } } void mergeSuccess ( MergePolicy . OneMerge merge ) { } final synchronized boolean registerMerge ( MergePolicy . OneMerge merge ) throws MergeAbortedException , IOException { } final synchronized void mergeInit ( MergePolicy . OneMerge merge ) throws IOException { } private synchronized void _mergeInit ( MergePolicy . OneMerge merge ) throws IOException { } private void setDiagnostics ( SegmentInfo info , String source ) { }

Fix:
message ( ( ( ( "now<seq2seq4repair_space>merge\n<seq2seq4repair_space>merge=" + ( merge . segString ( directory ) ) ) + "\n<seq2seq4repair_space>index=" ) + ( segString ( ) ) ) ) ;